London, Jan 12 (IANS): British newspaper The Guardian has confirmed that hackers accessed some of its employees' data in the ransomware attack in December last year.

An internal email, seen by The Record, said that it is "now clear that we experienced a highly sophisticated cyber attack involving unauthorised third-party access to parts of our network, which appears to have been triggered by a phishing attack."

The cyber attack was described as affecting many of the company's key systems, the IT network and "some" of its data.

The Guardian said it was a criminal ransomware attack.

"We have seen no evidence that any data has been exposed online thus far and we continue to monitor this very closely," said the news organisation.

The Guardian warned UK staff that attackers had accessed their sensitive personal information.

In December, the leading UK-based newspaper confirmed its systems have been hit by a "serious IT incident".

The publication said the cyber attack affected parts of the company's IT infrastructure.

"Online publishing is largely unaffected, with stories continuing to be written and published to the Guardian website and app," wrote the media editor at the publication.

Guardian Media Group Chief Executive Anna Bateson and Editor-in-Chief Katharine Viner said in a note to employees that "We believe this to be a ransomware attack but are continuing to consider all possibilities."

In September last year, hackers breached the internal systems of US business publication Fast Company.

In October, The New York Post also confirmed that it was hacked.